It has been referred to the Independent Police Complaints Commission (IPCC).

No charges have been made.

'Unresponsive'

Levers, from the Honicknowle area of the city, was pinned down by customers before police arrived, when he was found to be unconscious.

He died a short time later at the scene.

In a statement Ch Supt Andy Bickley said: "I can share with you that the firearm has been initially examined by a police firearms officer and it appears to be an imitation pistol, though this still needs to be verified.

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Ch Supt Andy Bickley said it would have been difficult to recognise the firearm as imitation

"I would like to add however that there would have been no way of knowing this at the time of the incident.

"The actions taken by members of the public in the shop were brave and showed a disregard for their own safety."

After he was restrained Levers was resuscitated by the police and ambulance service but he was declared dead about 20 minutes later.

Earlier, Ch Insp Ian Drummond-Smith told the BBC: "Customers and staff tackled the man, overpowered him, disarmed him and restrained him and when police officers arrived they found him being restrained but noted that he was unresponsive and wasn't breathing."

A spokesman for Ladbrokes said the company was assisting police.

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Eyewitness David Marfleet said it was a surprise the incident had occurred in such a "nice quiet area"

David Walker, 55, from West Park, Plymouth, said he walked into the bookmakers about five minutes after the incident.

He said: "When I went in there, they were scuffling on the floor, I just thought it was just a fight or something.

"There were the two men, customers I think, on top of him, and the bloke on the floor.

"I didn't see their faces, as they were holding the guy down at the back of the shop. I couldn't see any mask and there wasn't any physical movement, they were just holding him."

David Marfleet said: "[There were] easily 10 police cars and then two riot vans and then the ambulance that turned up on site as well.

"We don't normally have any trouble around here, it's quite a surprise it being such a nice quiet area."